This invention relates generally to medical devices, and more particularly to embolization devices, that is, devices for occluding a portion of the vascular system of a human or veterinary patient.
Embolization of vascular occlusion devices (hereinafter generally referred to as xe2x80x9cvasoocclusion devicesxe2x80x9d) are surgical implements or implants that are placed within the vascular system of a patient. Vasoocclusion devices are typically used either to block the flow of blood through a vessel by the formation of an embolus in the vessel, or to form such an embolus within an aneurysm stemming from the vessel. Such devices are conventionally introduced into the vascular system of the patient by a catheter, and can include a mechanical interlock to permit detachment of them from a pusher extending through the catheter.
A variety of prior implantable, coil-type vasoocclusion devices are known which include a coil having a lumen defined therein, and some kind of safety wire disposed in and extending through the lumen. The coils of such devices may themselves be formed into a secondary coil shape, or any of a variety of more complex secondary shapes adapted to the particular location at which an embolism or occlusion is to be established. A variety of thrombogenic materials may be attached to or carried by the coils of such devices to promote the formation of clots (thus, in turn, promoting the establishment of the embolism or occlusion), such as Dacron, polyester, silk or cotton fibers, filaments or the like. The coil itself, or the secondary coil shape, abuts or engages the wall of the vessel in which the device is disposed, serving to anchor the device in the vessel of interest.
For example, U.S. Pat. No. 4,994,069 to M. Ritchart et al., issued Feb. 19, 1991, discloses a flexible, coiled wire for use in small vessel occlusion. The wire has a stretched, linear condition in which it can be advanced through a catheter lumen to a selected vessel, and a relaxed, convoluted condition produced by a combination of helical windings of the wire and irregularities of the helical winding (referred to as a xe2x80x9cmemoryxe2x80x9d). The patent does not appear to suggest that the wire can itself be a conventional shape memory material, such as nitinol alloy.
Numerous similar devices have been disclosed. U.S. Pat. No. 5,749,891 issued May 12, 1998 and U.S. Pat. No. 5,582,619 to issued on Dec. 10, 1996, both to C. G. M. Ken et al., are directed to implantable vasoocclusion devices comprising a helically wound coil which is itself wound into a secondary shape. The devices can include an inner, stretch-resisting member positioned in the lumen of the coil. Possible materials for the wire making up either the coil or the inner member include stainless steel and nitinol. The device shown in FIG. 4 of the ""891 patent can include multiple layers of coils, the inner member being a wire which prevents stretching of the coil during movement of it. The ""619 patent also discloses a coil having a wire positioned therein to similarly prevent stretching.
U.S. Pat. No. 5,645,558 issued Jul. 8, 1997 to J. A. Horton, in FIG. 4 discloses a vasoocclusion device having a helical coil with a safety wire positioned therein for structural support. Alternatively, the internal wire may be preformed into an ultimately desired shape (for example, a sphere) and fed through the coiled strand, the coiled strand then assuming the shape of the safety wire.
Finally, FIG. 4 of U.S. Pat. No. 5,522,822 issued Jun. 4, 1996 to J. J. Phelps et al., discloses a vasoocclusion device which comprises a helical coil having an internal wire attached to end caps at both ends of the coil. The wire may be made of a shape memory material such as nitinol, while the coil is typically made of a radiopaque material such as tungsten, platinum, gold or silver.
The coil-type vasoocclusion devices in the last four of these patents can all be generally characterized in that the proximal and distal ends of the safety wire are affixed or directly secured to the respective proximal and distal ends of the coil itself. Each of these devices is of course subject to its own advantages and drawbacks during use. In general, however, and without ascribing this drawback to any of the devices disclosed in these particular patents, commercially available vasoocclusion coils do not anchor well in the target vessel and/or do not attain a shape which effectively occludes blood flow when deposited in the target vessel. This is because the only thing by which such commercially available coils apply an anchoring force against the wall of the target vessel, is the abutment force provided by the resilient return of the coils themselves to a desired shape.
It would be highly advantageous to have a coil-type vasoocclusion device in which the assistive force provided by the core to anchor the device at the location of interest, could be adjusted or selected to provide an optimal total anchoring force for the device. It would also be highly advantageous to have a coil-type vasoocclusion device which maximizes the assistive force provided by the core to anchor the device at the location of interest. It would further be highly advantageous to have a coil-type vasoocclusion device which could more readily be removed or repositioned than could prior coil-type vasoocclusion devices.
The foregoing problems are solved and a technical advance is achieved in an illustrative vasoocclusion device. More particularly, the deviceof the present invention is directed to a rapidly and reliably deployable and repositionable, self-anchoring, mechanical vascular occluder whose shape and anchoring force are predetermined by an included core having a shape memory. The device of the present invention is a coil-type vasoocclusion device having a coil with a coil lumen defined therein, the core being disposed in part or more of the coil lumen. The core can be composed of a nitinol or other shape memory material, preferably in a superelastic state, or can be composed of stainless steel, MP35N or the like. (If nitinol material is used, the nitinol need not be in its stress induced, martensite condition, however, and preferably is not in such a condition.) The core is xe2x80x9cspringyxe2x80x9d and provides an additional, anchoring assistive force, which supplements the anchoring force provided by the coil itself and which can improve the effectiveness of the coil in several applications. The present invention can be further characterized in that, unlike comparable coil-type devices, the nitinol or other shape memory material core is not affixed to the coil at both of its ends. Instead, only one portion of the core is affixed to the coil, preferably one end of the core being affixed at or near one end of the coil, while the remainder of the core is not affixed to the coil.
Such an arrangement of fixing the core to the coil may advantageously allow an adjustment of the assistive anchoring force provided by the core to a coil of a given length, by selection of the length of the core. Such an arrangement may also maximize the assistive anchoring force provided by the core, since such force would not be diminished by any twisting of the core during manipulation or positioning of the coil. Further, such an arrangement may facilitate removal or repositioning of the device, since elongation of the coil when subjected to a longitudinal removing force may lessen the anchoring force supplied by the coil itself, making engagement with the introducing or removal apparatus easier.
In a first aspect, then, the present invention is directed to a vasoocclusion device for establishing an embolus or vascular occlusion in a human or veterinary patient, the device comprising: a coil having a proximal coil end, a distal coil end spaced from the proximal coil end and a coil lumen defined therein extending between the proximal coil end and the distal coil end; and a core disposed in at least part of the coil lumen, the core having a proximal core end and a distal core end; and wherein one portion of the core is affixed to the coil at a selected location, whereby the core provides the coil with an anchoring force in a vessel of the human or veterinary patient.
Preferably, the coil lumen possesses a defined cross-section, and the core can but need not substantially fill the defined cross-section of the coil lumen. Also preferably, the distal core end is directly affixed to the distal coil end in any convenient manner, for example, by solder, welding or adhesive.
The diameter of the core is selected so as to provide a desired assist to the expansile or anchoring force of the coil. Such force can be adjusted over a relatively wide range. The core can extend through the entire lumen of the coil, or can instead extend in only part of the lumen, for example, from either the proximal or distal end of the coil. This leaves the remaining part of the coil highly flexible, or xe2x80x9cfloppy.xe2x80x9d
In certain embodiments, the core has a changing diameter. In one, the core tapers toward its free end, that is, an end which is not affixed to the respective coil end; by using a tapered nitinol wire, the assistive forces of the coil can be even more precisely adjusted along the coil. In another, both end-portions of the core are tapered; as a result, the coil""s expansive force will be the greatest at its mid-portion, while the coil strength will be evenly reduced toward the ends. Consequently, it is the mid-portion of the coil that will mostly anchor the device within the vasculature while the moderately reinforced end-portions allow for better coverage of the center space of the vessel resulting in quicker occlusion.
In a further embodiment, the core is formed from a nitinol wire whose diameter alternates between a larger and a smaller caliber, and the transition between the larger and smaller caliber segments is even and continuous without step formation. This technical solution makes it possible to use relatively great assistive forces to anchor the device, but simultaneously preserves the pliability or flexibility of the coil to a certain degree, facilitating both the proper arrangement of coil turns within the vasculature and pushability of the coil through the delivery catheter.
The vasoocclusion device is preferably adapted for introduction into the patient via a catheter, the device being detachably secured to the catheter. More particularly, the device is preferably adapted for introduction via a pusher contained in the catheter, and the device further comprises a reversible coupling for detachably connecting the device to the pusher.
As indicated, the core preferably comprises nitinol, another shape memory material, stainless steel or MP35N. The nitinol is preferably in a superelastic state, but is in a condition other than its stress induced, martensitic condition.
The coil of the vasoocclusion device can comprise any convenient non-linear secondary shape upon its deployment in the patient. The secondary shape can be a saddle-type, helical type, vortex-type, irregular baffle-type, fusiform helix-type or oval plate shape. It may also be spherical, derived from circular or D-shaped or semicircular shapes of the helical turns. The vasoocclusion device preferably further comprises a thrombogenic material connected to or carried by the coil, such as Dacron, silk, cotton, wool or polyester threads.
In a second aspect, the present invention is directed to a specific combination of the features mentioned above. More particularly, it is directed to a vasoocclusion device for establishing an embolus or vascular occlusion in a human or veterinary patient, the device being adapted for introduction into the patient via a catheter, and the catheter having a pusher contained therein for deploying the device from the catheter; the device comprising: a coil having a proximal coil end, a distal coil end spaced from the proximal coil end and a coil lumen defined therein extending between the proximal coil end and the distal coil end; a core disposed in at least part of the coil lumen, the core having a proximal core end and a distal core end; and a thrombogenic material connected to or carried by the coil; wherein the distal core end is affixed to the distal coil end by solder, welding, or an adhesive; wherein the core comprises nitinol in a superelastic state, being in other than its stress induced, martensitic condition; wherein the thrombogenic material comprises Dacron, cotton or polyester threads; wherein the coil (12) comprises a wire (14) having a diameter of about 0.010 in. to about 0.032 in. (about 0.25 mm to about 0.81 mm); wherein the core (22) has a diameter of about 0.004 in. to about 0.015 in. (about 0.10 mm to about 0.38 mm); wherein the coil (12) is about 2 to about 40 cm long when constrained within a catheter; and wherein the core provides the coil with an additional force assisting anchoring of the coil in the human or veterinary patient when the coil and the core are deployed from the catheter.
In a third aspect, the present invention is directed to the combination of the coil and core device with the catheter and pusher for deploying the device in the patient. Thus, in its third aspect, the present invention is directed to a medical device for establishing an embolus or vascular occlusion in a human or veterinary patient, comprising: a coil having a proximal coil end, a distal coil end spaced from the proximal coil end and a coil lumen defined therein extending between the proximal coil end and the distal coil end; and a core disposed in at least part of the coil lumen, the core having a proximal core end and distal core end; wherein one portion of the core is affixed to the coil at a selected location; a catheter dimensioned to receive the coil and the core therein; and a pusher contained in the catheter, adapted to deploy the coil and the core from the catheter; wherein the core provides the coil with an additional force assisting anchoring of the coil in the human or veterinary patient when the coil and the core are deployed from the catheter. This third aspect of the present invention preferably further comprises a coupling for detachably connecting the coil to the pusher.
In a fourth and final aspect, the present invention is directed to an improvement in a coil-type vasoocclusion device for establishing an embolus or vascular occlusion in a vessel of a human or veterinary patient, the device comprising: (a) a coil having a proximal coil end, a distal coil end spaced from the proximal coil end, a coil lumen defined therein extending between the proximal coil end and the distal coil end; and (b) a core disposed in at least part of the coil lumen, the core having a proximal core end and a distal core end; the improvement being characterized in that one and only one of the proximal core end and the distal core end is affixed to the coil proximate to a respective one of the proximal coil end and the distal coil end, the other of the distal core end and the proximal core end not being affixed to either the distal coil end or the proximal coil end; and wherein the core provides the coil with an anchoring force in the vessel.
As indicated above, the vasoocclusion device of the present invention may possess significant advantages over prior coil-type vasoocclusion devices. It may be possible to adjust the assistive anchoring force provided by the core to a coil of a given length, by selection of the length of the core. Since one end of the core is free and not affixed to an end of the coil, the assistive anchoring force provided by the coil may be maximized, and not diminished by any twisting of the core during manipulation or positioning of the coil. Finally, such an arrangement may facilitate removal or repositioning of the device, since elongation of the coil when subjected to a longitudinal removing force may lessen the anchoring force supplied by the coil itself, making engagement with the introducing or removal apparatus easier. Of course, in contrast to comparable stainless steel coils lacking the nitinol or other core, the vasoocclusion device possesses significantly enhanced self-anchoring capability, which is expected to result in the substantial reduction or elimination of migration of the installed coil. Further, however, the vasoocclusion device is rapidly and readily repositionable after deployment in a patient. Advantageously, the vasoocclusion device can often be deployed into a patient through the same catheter as is used for comparably-sized stainless steel coils.